As new technologies are implemented to produce smaller semiconductor device components, there is increasing interest in the use of alternative p-type and n-type dopants. For example, antimony and indium are being considered as a replacement for boron at certain stages of device fabrication, such as the construction of the source and drain extensions and halo structures. The implantation of such materials raises a number of process fabrication challenges, however.
For instance, for the implantation of indium, a preferred source material is indium trichloride. Indium trichloride is desirable because it vaporizes at a substantially lower temperature than other potential source materials such as indium oxide, and it does not require a carrier gas. In comparison, when using indium oxide as the source material, an organic carrier gas, such as carbon tetrachloride, is required.
The use of indium trichloride has been problematic however. To provide a constant supply of source material to the arc chamber of an ion implanter device, the source material typically vaporizes in a vaporizing chamber. The vaporizing chamber is initially degassed by applying a vacuum. When using indium trichloride as the source material, it can take several hours to perform this degassing operation. Moreover, it is difficult to maintain a steady low pressure during degassing. Sometimes the vacuum can be lost, requiring the entire process to be restarted. Furthermore, indium trichloride powder is prone to movement within the chamber during degassing. This, in turn, can result in longer chamber cleaning times after ion implantation, as well as the contamination of other components of the ion implanter. Similar problems exist with antimony trichloride.
Therefore, there is a need for an improved source material for ion implantation in semiconductor devices that avoid the above-mentioned limitations.